You've done the right thing and got three quotes. Now they're in front of you and they look nothing like each other — different panel brands, different inverters, different system sizes, wildly different prices. How do you compare them properly?
First: Make Sure You're Comparing the Same Thing
The most common comparison mistake is quoting different system sizes. A 6.6kW quote from one company is not comparable to a 8.5kW quote from another unless you adjust for size. Ask all three companies to quote you the same system size (say, 6.6kW) with equivalent-tier components, so you can isolate the price difference to the company and the equipment quality — not just the panel count.
The One Number That Cuts Through: Cost Per Watt
Divide the total installed price (post-STC rebate, including all extras) by the system size in watts. A 6.6kW system at $6,600 costs $1.00 per watt. A 6.6kW system at $8,250 costs $1.25 per watt.
In 2026, a reasonable price range for a quality 6.6kW system in most Australian capitals is $0.90–$1.30 per watt (installed, post-rebate). Under $0.90/W is suspicious — either the components are low-grade or someone's cutting corners on installation. Over $1.50/W without a clear premium reason (microinverters, complex roof, premium brand) warrants scrutiny.
What to Check in Every Quote
Panels
Get the exact model number (e.g., "LONGi Hi-MO 7 440W") not just the brand. Look up whether the brand is Tier 1 rated by BNEF. Check the product warranty (12 years minimum; 25 years is better) and the performance warranty (80% at 25 years is the standard; 85%+ is premium).
Inverter
The inverter is the component most likely to need replacement within your system's life. Reputable brands: Fronius, SMA, SolarEdge, Sungrow, Enphase. Check the warranty — 5 years standard, 10–15 years for premium brands. If you're planning to add a battery later, verify whether the quoted inverter is battery-ready (hybrid).
Installation
Is the installer CEC-accredited (the person actually going on your roof, not just the company)? Does the quote include all electrical work, roof penetration sealing, metering changes, and network application fees? Ask specifically what's not included.
Workmanship Warranty
Minimum 5 years for CEC Approved Retailers. Aim for 10 years. This is separate from the panel and inverter warranties, and it covers installation faults.
Hidden Costs to Watch For
- Switchboard upgrade: If your switchboard is old or doesn't have a spare circuit, an upgrade ($500–$1,500) may be needed and not included in the quote.
- Scaffolding: Two-storey homes or steep roofs may require scaffolding ($300–$800) — ask if this is included.
- Smart meter: Some retailers require a smart meter for solar feed-in — this may involve a cost or a longer wait for your first export payment.
- Feed-in tariff applications: Check who handles the network application. Most good installers handle this. Some don't.
The Savings Estimate
Every quote should include an annual savings estimate. Don't just accept it at face value — ask what assumptions it's based on. What daily usage did they assume? What feed-in tariff rate? What self-consumption percentage? A quote with a very high savings estimate may be using optimistic assumptions to make their price look better.
Cross-check it against an independent estimate. Upload your electricity bill to GridBeater and we'll give you an unbiased savings calculation based on your actual usage — a useful sanity check on what the installers are telling you.
Get an independent savings estimate before you decide → Free at GridBeater